(a) Field of the Invention
The present invention relates to a stabilized vitamin C derivative having a peptide molecule or a pharmaceutically acceptable salt thereof, a preparation method of the vitamin C derivative, and a composition containing the same.
(b) Description of the Related Art
Skin plays the roles of protection, barrier, body temperature regulation, excretion, respiration, and so forth, and consists of epidermis, dermis, and hypodermis. The epidermis is the thinnest layer, consisting of keratinocytes and melanocytes. The dermis accounts for about 95% of skin and is the layer that takes up skin moisturization and protection. It consists of collagen and elastin, which are protein fibers that play important roles in skin elasticity (or wrinkles). The dermis contains blood vessels, nerves, mast cells associated with allergic reactions, and natural moisturizing factors such as Na-PCA, hyaluronic acid, etc. The hypodermis supplies nutrients to the epidermis and the dermis, determines body shape, maintains body temperature, absorbs external impact, and protects the cells therebelow.
As skin ages, its functions decline rapidly because of endogenous or exogenous factors. As aging proceeds, the layers of the epidermis, the dermis, and the hypodermis become thin, and the collagen and elastin fibers become thinner and less elastic, resulting in wrinkles. Further, as the lipid composition and content in the lipid barrier that protects the skin changes, the moisture content in skin decreases, resulting in dryness and other physiological changes. Furthermore, melasma, freckles, pigmentation, and various other skin lesions are induced. In order to solve the skin aging-related problems, much research has been carried out on various active substances effective in skin improvement, and compositions containing them.
Antioxidant vitamins, such as vitamin C, vitamin E, β-carotene, and so on, have been used to inhibit skin aging. Among them, vitamin C is known to be effective in improving skin wrinkles, improving pigmentation problems such as melasma, freckles, dark spots, etc., and enhancing the immune system through protection from UV, antioxidant activity, and promotion of collagen formation. The functions of vitamin C in the body are as follows.
Vitamin C effectively blocks UV, particularly UV A [Darr, D. et al., 1996, Acta Derm. Venereol. (Strckh). 76: 264-268; Black, H. S. et al., 1975, J. Invest. Dermatol. 65: 412-414]. Also, vitamin C protects the skin from damage induced by UV B. When vitamin C is applied on the skins of pigs and humans and then UV B is irradiated thereon, it prevented erythema and sunburn (Darr, D. et al., 1992, Brit. J. Dermatil. 127: 247-253; Murry, J. et al., 1991, J. Invest. Dermatol. 96: 587).
Vitamin C acts as a strong antioxidant, which neutralizes the reactive oxygen species (ROS) generated in skin, blood, and other tissues by chemical contaminations, smoking, and particularly, UV. This is because of the structural characteristics of the vitamin C, which can accept two electrons and be readily oxidized to dehydro-L-ascorbic acid. Vitamin C is an important factor in the non-enzymatic antioxidant defense system of skin. When present in high concentration, vitamin C neutralizes such ROS as singlet oxygens, superoxide anions, hydroxy radicals, etc., before they oxidize or modify proteins, nucleic acids, cytoplasmic membrane lipids or other body constituents (Buettner, G. R. et al. 1996. Cadenas, E., Packer, L., eds. Handbook of antioxidants. pp. 91-115).
When administered percutaneously to the stratum corneum, vitamin C improves skin gloss and skin color, reduces wrinkles, and improves skin elasticity (U.S. Pat. No. 4,983,382), because it promotes collagen synthesis. Hydroxyproline, which accounts for about 10% of collagen polypeptides, is synthesized by proline hydroxylase, wherein vitamin C acts as a cofactor of this enzyme (Tomita, Y. et al., 1980, J. Invest. Dermatol. 75(5): 379-382). That is, vitamin C activates proline hydroxylase to promote the synthesis of hydroxyproline, which in turn promotes the biosynthesis of the triple-helical collagen, thereby reducing skin wrinkles and improving skin condition.
Vitamin C offers a superior skin whitening effect, because it inhibits the activity of tyrosinase, which is important in producing melanin, and the production of melanin (Tomita, Y. et al., 1980, J. Invset. Dermatol. 75(5); 379-382).
In addition, vitamin C enhances the immune system by inhibiting the release of allergy-inducing histamine from the cell membrane, thereby preventing allergic reactions. It has been proven that vitamin C protects mice exposed to antigens from UV-induced immune suppression and resistance (Nakamura, T. et al., 1997, J. Invest. Dermatol. 109: 20-24).
Further, vitamin C helps the phagocytosis of leukocytes, facilitates the movements of leukocytes during infection to inhibit infection, promotes the biosynthesis of interferon, which is a protein that suppresses the proliferation of viruses, and improves resistance to a variety of infectious diseases. Further, vitamin C also participates in folic acid metabolism and amino acid metabolism.
Vitamin C is a water-soluble substance with the chemical formula C6H8O6. Vitamin C is hydrophilic because of the hydroxyl groups present in C-2, C-3, C-5, and C-6 positions. In neutral pH, e.g., in water, the hydroxyl groups, particularly those in C-2 and C-3 positions, in Vitamin C becomes negatively charged, to be quickly and completely dissolved in aqueous solutions. However, under non-aqueous organic environments, e.g., in skin, vitamin C is not completely dissolved. Further, because vitamin C is not readily dissolved in the organic solvents commonly used in the external preparations, e.g., glycerin, propylene glycol, a variety of fats, etc., transdermal delivery of vitamin C is restricted. That is, in a non-ionized state, the pH should be maintained at 4.2 or lower in order for vitamin C to easily penetrate the skin barrier.
It is known that vitamin C is accumulated in skin 20 to 40 times higher when transdermally (externally) administered than orally administered. External preparations for improving wrinkles by UV blocking, antioxidation and promotion of collagen production, improving pigmentation problems such as melasma, freckles, dark spots, etc., and enhancing the immune system, should have a high degree of transdermal absorption because the active ingredients of the preparations need to reach the cells in the epidermis by passing through the stratum corneum of skin. In general, the degree of transdermal absorption of a substance relates to its lipophilicity. It is known that a substance having lipophilicity similar to that of skin is readily absorbed transdermally, because the partition coefficient into skin is high. In contrast, vitamin C is not readily absorbed transdermally because of high hydrophilicity and a low partition coefficient into skin.
There has been much research to improve safety, stability, and transdermal absorptivity of vitamin C.
Several types of vitamin C derivatives have been suggested. The first type of derivative is a phosphated ascorbic acid or a metal salt of phosphated ascorbic acid. This derivative is obtained by linking the hydroxyl group of the C-2 or C-3 position of ascorbic acid through an ester bond with the phosphate to form ascorbyl-2-phosphate or ascorbyl-3-phosphate, respectively. Compared with other derivatives, these derivatives are easily transited to L-ascorbic acid that can be utilized by the human body. However, they are not readily absorbed transdermally because they have negative charges.
The second type of derivative is an ascorbic acid bonded to a fatty acid. U.S. Pat. No. 5,409,693 discloses a vitamin C derivative in the form of a fat-soluble fatty acid ester of ascorbic acid, such as ascorbyl palmitate, ascorbyl laurate, ascorbyl myristate, ascorbyl stearate, etc. Among them, ascorbyl-6-palmitate is most frequently utilized. Although ascorbyl-6-palmitate is readily absorbed transdermally, it is not readily transited to L-ascorbic acid. It is reported that ascorbyl-6-palmitate failed in protecting the skin of mice from photo-oxidation (Bissett, D. et al., 1990, Photodermatol Photoimmunol Photomed 7: 56-62). There is another report that the treatment of skin with a serum containing 10 wt % ascorbyl-6-palmitate did not result in a significant increase of ascorbic acid (Pinnell, S. R. et al., 2001. Dermatologic Surgery. 27(2): 137-142).
The third type of derivative is ascorbic acid derivatives having a monosaccharide, such as glycosylated, mannosylated, fructosylated, fucosylated, galactosylated, N-acetylglucosaminated, or N-acetylmuraminated form. However, the physiological activities of these derivatives in the body have not yet been elucidated specifically and accurately.
The fourth type of derivative is an ascorbic acid bonded with a collagen-producing peptide. Korean Patent No. 0459679 discloses a derivative obtained by linking the hydroxyl group of the C-5 or C-6 position of ascorbic acid with a succinoyl group through an ester bond, and linking it with a collagen-producing peptide through an imide bond. This ascorbic acid derivative shows better efficiency than ascorbic acid, but is less stable.
Collagen is frequently found in skin, blood vessels, internal organs, bones, etc. It accounts for 70% of the dermis in skin. The fascia which surrounds muscles is made up of collagen. Collagen, which accounts about 30 wt % of the total proteins in the body, offers mechanical solidity to skin, confers resistance and binding strength of connective tissues, supports cell adhesion, and induces cell division and differentiation during growth or healing of wounds. Collagen is produced in fibroblasts. The amount of collagen decreases with natural aging and photo-aging. It is known that the amount of collagen decreases by 65% from the age of 20 to 80 (Shuster S., 1975, British Journal of Dermatology, 93(6): 639-643).
With the finding that activated collagen synthesis in the body increases the dermal matrix, resulting in the effects of improving wound healing, skin elasticity, wrinkle reduction, etc., collagen has been utilized in cosmetics, foods, medicines, and so forth. Some oligopeptides having less than 10 amino acids, which exist in collagen, are the smallest activation unit. They relate to functions as messenger, stimulator, and neurotransmitter, and take part in such physiological metabolisms as growth control, nursing, immunity, digestion, blood pressure, and healing. Particularly, peptides that are effective in skin regeneration are disclosed in French Patent No. 2,668,265, U.S. Pat. No. 4,665,054, WO91/3488, WO91/7431, and so forth. However, these peptides tend to form precipitates, thereby greatly reducing product stability.
Thus, the development of vitamin C derivatives with improved safety and stability and superior skin permeability is needed.